Cellulose fiber

ABSTRACT

The present invention relates to a cellulose fibre which is characterized by a biodegradation rate of less than 60% after 20 weeks and/or in which the note for the susceptibility to  Eurotium rubrum  amounts to less than 2 after 4 weeks at an air humidity of 85%.

The present invention relates to a cellulose fibre with a reduced biodegradation rate as well as a reduced susceptibility to moulds.

It is known to impart antimicrobial properties to cellulose fibres by means of additives.

From U.S. Pat. No. 3,296,000 it is known to modify viscose fibres with 3,4,4′-trichlorocarbanilide in order to achieve bacteriostatic properties.

EP-A 0 728 855 describes the manufacture of fibres of various origins, among other things, cellulose fibres having deodorizing properties. Thereby, photocatalysts, in particular titanium oxide (TiO₂), are used. In addition, an adsorbent in the form of a phosphate of a tetravalent metal and of a hydroxide of a divalent metal is used. EP-A 0 728 855 furthermore describes that, in addition to the substance having a deodorizing effect, a metallic component (f.i. silver, copper or zinc) may be used as an antimicrobial component.

From the market survey “Functional Fibers—Trends and Product Development in Japan” of Toray Research Center Inc., 1993, viscose fibres which are said to exhibit antibacterial and odour-reducing properties are known under the brand names “CELFRESH”, “PC Rayon”, “CELBEL” and “CELCLEAN”.

In case of the fibre “CELFRESH”, activated carbon in an amount of approx. 30% is added to the viscose. In case of the fibre “PC Rayon”, a metal phthalocyanine derivative is added to the viscose. Regarding the fibres “CELBEL” and “CELCLEAN”, metal ions are applied onto the already spun fibres during the aftertreatment process.

However, the use of activated carbon or of metallic components involves the drawback that those components, as becomes apparent also, for example, from the above-quoted market survey, are dyed and therefore have a negative impact on the whiteness of the resulting fibre. In particular in the so-called Lyocell process for the manufacture of cellulosic fibres, the additional problem arises that many metallic components reduce the stability of the cellulose solution.

The use of chitosan in order to give deodorizing and/or fungicidal properties or bacteriostatic properties, respectively, to cellulosic regenerated fibres is also known, for example, from U.S. Pat. No. 5,320,903 or from PCT-WO 94/09192.

Furthermore, it is known to furnish fibres or textile products with antimicrobial agents.

A disadvantage of additives or finishings consists in the possible toxicological and also ecological effects, for example by allergic reactions or also due to the release into the environment when washing the products produced therefrom.

Environments exhibiting an increased air humidity promote the growth of microorganisms, in particular of moulds, for instance in beddings, in particular in fillings for bed linen and pillows. Those moulds also form the nutritional basis for mites.

Therefore, there still exists a demand for cellulosic fibres having biocidal properties, which, in addition, are skin-compatible.

The present invention provides a cellulose fibre which is characterized by a biodegradation rate of less than 60% after 20 weeks (measured in accordance with the soil-burying test described below). Preferably, the cellulose fibre according to the invention has a biodegradation rate of less than 40%, particularly preferably of less than 30%, after 20 weeks.

Furthermore, the present invention provides a cellulose fibre which is characterized in that the note for the susceptibility to Eurotium rubrum amounts to less than 2 after 4 weeks (measured according to the test described below, mean value from three measurements) at an air humidity of 85%. Particularly preferably, the note for the susceptibility to Eurotium rubrum amounts to 1 or less after 4 weeks at an air humidity of 85%.

Preferably, the cellulose fibre according to the invention exhibits both the above-indicated degradation rate and the above-indicated note for the susceptibility to Eurotium rubrum.

The cellulose fibre according to the invention is preferably characterized in that it is a fibre of the Lyocell type.

Furthermore, the cellulose fibre according to the invention is preferably characterized in that it is basically free from antimicrobial substances. “Basically free” means that the fibre does not contain any additional antimicrobial agents apart from substances which are contained in the fibre as a result of the normal conditions of the respective manufacturing process and which possibly also display an antimicrobial activity.

Surprisingly, it has been found that, in case of Lyocell fibres, the growth of microorganisms is delayed or prevented, respectively, in comparison with other cellulosic fibres such as cotton or viscose fibres.

In solvent-spinning processes, the cellulose is dissolved directly in an organic solvent without the formation of a derivative and the solution is spun. Such fibres are also referred to as “solvent-spun” or “Lyocell” fibres. “Lyocell” is the generic name allocated by BISFA (The International Bureau for the Standardization of man made fibers) for cellulose fibres which are produced by dissolving cellulose in an organic solvent without the formation of a derivative and extruding fibres from said solution by means of a dry-wet spinning process or a melt-blown process. An organic solvent is thereby understood to be a mixture of an organic chemical and water. At present, N-methyl-morpholine-N-oxide is used as an organic solvent on a commercial scale.

In said process, the solution of the cellulose is usually extruded by means of a forming tool, whereby it is moulded. Via an air gap, the moulded solution gets into a precipitation bath, where the moulded body is obtained by precipitating the solution. The moulded body is washed and optionally dried after further treatment steps. A process for the production of Lyocell fibres is described, for instance, in U.S. Pat. No. 4,246,221. Lyocell fibres are distinguished by a high tensile strength, a high wet-modulus and a high loop strength.

The present invention also relates to the use of the cellulose fibre according to the invention for the manufacture of yams, fabrics, knitted fabrics, nonwovens and other textile articles. In particular, the invention relates to the use of the fibre according to the invention as a component of home textiles such as, for example, blankets, pillows, furniture, mattresses, towels, bed linen, in particular as a filling fibre in blankets, pillows, mattresses and furniture.

Furthermore, the present invention relates to a textile article, for instance a home textile, which contains the cellulose fibre according to the invention.

Preferably, the textile article according to the invention contains an amount of cellulosic material of at least 10% by weight. In case of furniture, said amount refers to the textile components (cover etc.) of the piece of furniture.

Preferably, the cellulosic material in the textile article contains the cellulose fibre according to the invention by 30 to 100% by weight.

Textile articles containing the cellulose fibre according to the invention are particularly suitable as bioactive products.

For the purposes of the present invention, “bioactive” is understood to be the delay or prevention, respectively, of the growth of microorganisms.

Due to the resistance of the cellulose fibre according to the invention to moulds, mites and the like are deprived of their nutritional basis. Therefore, textile articles according to the invention are particularly suitable also as anti-mite products.

EXAMPLES

Biodegradability

Lyocell fibres (CLY) were compared with cotton (BW) and viscose fibres (CV) in a soil-burying test. In comparison with other cellulose fibres such as BW and CV, Lyocell fibres show a clearly delayed degradation behaviour or bioactivity, respectively.

Soil-burying Test:

Approx. 1 g of carded air-dry nonwoven fabrics (approx. 6×6 cm) are placed in a coarse-meshed bag of synthetic fabric (mosquito net) and sealed with adhesive tape.

The samples are buried in a container (flower box approx. 100×20×15 cm) centrally in horticultural soil (Spezial Humus, Messrs. Gartenhilfe GmbH 4030 Linz) and are set up in the dark at room temperature (20-25° C.). The soil is kept moist by irrigation with tap water. At certain intervals, the samples are dug out, dried and weighed. Throughout the observation period, the degradation factor is determined by weight detection as well as optically.

The results are illustrated in the follwing table: % of degradation after weeks Fibre 2 4 8 12 16 20 Cotton 34 52 77 88 94 100 (BW) Viscose 10 48 57 61 64 69 (CV), 6.7 dtex Lyocell 11 14 15 19 21 28 (CLY), 6.7 dtex SI Lyocell 9 12 13 15 16 20 (CLY), 6.7 dtex

The Lyocell fibre indicated by “SI” is a Lyocell fibre furnished with silicone.

If the viscose fibre having a titre of 6.7 dtex is compared to the Lyocell fibres also having a titre of 6.7 dtex, a difference in the degradation rate of 40-50% will appear after 20 weeks.

It turns out that the biodegradation rate of Lyocell fibres is by 50% lower than that of viscose and by 80% lower than that of BW.

Testing Fibres for Their Susceptibility to Moulds

The trials described below were carried out at the EMPA (Eidgenössische Materialprüfungsund Forschungsanstalt).

The test is performed according to rule CEN/TC 248/WG13/Doc N 142-Method A2, wherein the growth of the mould fungus “Eurotium rubrum” is observed at room temperature and at an air humidity of 75, 85 and 100%.

The humidity in the moist chamber was adjusted by NaCl for 75% KCl for 85% and water for >95%.

Eurotium rubrum EMPA 633 was generally used as the fungus, the spore density of the inoculation amounted to 10⁶ per ml.

The fungal growth at the samples is evaluated by means of the following diagram: Growth rate (note) Assessment 0 No growth visible under the microscope (50-fold enlargement) 1 No growth visible with the naked eye, but clearly visible under the microscope 2 Growth visible with the naked eye, covers up to 25% of the test surface 3 Growth visible with the naked eye, covers up to 50% of the test surface 4 Substantial growth, covers more than 50% of the test surface 5 Strong growth, covers the entire test surface

As can be seen in the following table, a Lyocell fibre exhibits a clearly inhibited fungal growth relative to viscose fibres after 4 weeks at an air humidity of 85%. Eurotium rubrum Air humidity Sample 75% 85% 100% 1 CLY 6.7 dtex SI 0/0/0 0/1/1 5/5/4 2 CLY 6.7 dtex 0/0/0 0/0/0 5/4/1 3 CV 3.3 dtex 0/0/0 3/4/4 5/5/4 

1. A method for producing an antimicrobial effect in a textile article comprising cellulosic material, comprising manufacturing the textile article to include an antimicrobial substance consisting of Lyocell fiber to which no further antimicrobial substance has been added, wherein the amount of Lyocell fiber constitutes at least ten percent by weight of the textile article; and demonstrating the antimicrobial property of the article.
 2. The method of claim 1, wherein the antimicrobial property demonstrated is the reduced growth rate of a microbe.
 3. The method of claim 1, wherein the cellulosic material in the textile article contains between 30 and 100 percent Lyocell fiber.
 4. The method of claim 1, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 5. The method of claim 1, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 6. The method of claim 1, wherein the textile article is a blanket.
 7. The method of claim 1, wherein the textile article is a piece of furniture having a textile component.
 8. The method of claim 2, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 9. The method of claim 2, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 10. The method of claim 2, wherein the textile article is a blanket.
 11. The method of claim 2, wherein the textile article is a piece of furniture having a textile component.
 12. The method of claim 3, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 13. The method of claim 3, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 14. The method of claim 3, wherein the textile article is a blanket.
 15. The method of claim 3, wherein the textile article is a piece of furniture having a textile component.
 16. A method for reducing biodegradation of a textile article comprising cellulosic material, comprising manufacturing the textile article to comprise Lyocell fiber, wherein no further antimicrobial substance is added to the Lyocell fiber, and demonstrating a reduced degradation rate of the textile article.
 17. The method of claim 16, wherein the reduced degradation rate demonstrated is the reduced loss in weight of the article.
 18. The method of claim 16, wherein the cellulosic material in the textile article contains between 30 and 100 percent Lyocell fiber.
 19. The method of claim 16, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 20. The method of claim 16, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 21. The method of claim 16, wherein the textile article is a blanket.
 22. The method of claim 16, wherein the textile article is a piece of furniture having a textile component.
 23. The method of claim 17, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 24. The method of claim 17, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 25. The method of claim 17, wherein the textile article is a blanket.
 26. The method of claim 17, wherein the textile article is a piece of furniture having a textile component.
 27. The method of claim 18, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric and a non-woven fabric.
 28. The method of claim 18, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 29. The method of claim 18, wherein the textile article is a blanket.
 30. The method of claim 18, wherein the textile article is a piece of furniture having a textile component.
 31. A method for producing a mite-resistant textile article comprising cellulosic material, comprising manufacturing the textile article to include a bioactive product consisting of Lyocell fiber, wherein the amount of Lyocell fiber constitutes at least ten percent by weight of the textile article; and demonstrating the mite-resistance of the article.
 32. The method of claim 31, wherein the cellulosic material in the textile article contains between 30 and 100 percent Lyocell fiber.
 33. The method of claim 31, wherein the textile article is selected from the group consisting of a yarn, a fabric, a knitted fabric, and a non-woven fabric.
 34. The method of claim 31, wherein the textile article is selected from the group consisting of a pillow and a mattress.
 35. The method of claim 31, wherein the textile article is a blanket.
 36. The method of claim 31, wherein the textile article is a piece of furniture having a textile component. 